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SSH2 Subsystems

SSH2 subsystems are a useful convenience feature to predefine remote commands for SSH clients to invoke easily. Subsystems provide a layer of abstraction for defining and invoking the remote commands. A subsystem need not be a separate program; it can invoke a function built into the SSH server itself. SFTP is the most common SSH subsystem that you are going to encounter. For example on Linux distributions, the default /etc/ssh/sshd_config file defines one subsystem, This is the configuration line on Fedora 20: # override default of no subsystems Subsystem sftp /usr/libexec/openssh/sftp-server Do not remove or comment out the above line.

Exploring NetApp Simulate ONTAP

NetApp Simulate ONTAP is a simulator for running Data ONTAP software. It has been available for a number of years to NetApp customers and partners, and is readily obtainable (unofficially) from any number of websites. It enables you to test most features of Data ONTAP 7-Mode or Cluster-Mode, and is an excellent tool for learning about the features of Data ONTAP. There have been various versions of Simulate ONTAP over the years. Initially it had to be installed on a Red Hat or SuSE Linux platform but over the years more Linux distributions were added. Nowadays Simulate ONTAP is also

Perfect Forward Secrecy in SSH

Perfect Forward Secrecy (PFS) is a property of public-key encryption systems which generate random public keys per session for the purposes of key agreement which are not based on any sort of deterministic algorithm. A compromise of one message cannot lead to the compromise of another message or multiple messages. Twitter, Apache mod_ssh, SSL, TLS, and IPSec all support forward secrecy. According to the referenced Wikipedia article: Forward secrecy is designed to prevent the compromise of a long-term secret key from affecting the confidentiality of past conversations. However, forward secrecy (including perfect forward secrecy) cannot defend against a successful cryptanalysis

Fedora 18 Supports 256 Color Terminals

You may not be aware of it but currently Linux terminal emulators such as xterm only supports 8 colors while those on Apple’s OS X support 256 colors. Now, beginning with Fedora 18, Fedora will also support 256 colors via the xterm-256color terminfo database entry. To see how many colors a terminal supports: $ echo $TERM xterm-256color $ tput colors 256 I have never liked the default colors produced by the –color color option to ls and other utilities and, as a result, have normally removed such aliases from my bash startup scripts. Having 32 times more colors available gives

Using Expect to Transfer SSH Keys

TCL (Tool Command Language, typically pronounced as “tickle”) is a scripting language created by John Ousterhout in 1988 while working at the University of California, Berkeley. To provide additional functionality, TCL supports extensions. One of the most popular extensions is Expect which is a tool developed by Don Libes for automating and testing interactive applications such as ftp. telnet and ssh. I assume you know how to generate SSH keys using ssh-keygen and understand that if you want to be able to ssh to a remote system without entering a password you need to create the keys without a passphrase.